1. Field of the Invention
The present invention relates to a head suspension for a disk drive incorporated in an information processing apparatus such as a personal computer.
2. Description of the Related Art
A hard disk drive (HDD) records and reproduces information to and from rotating magnetic or magneto-optical disks. The HDD has a carriage turned around a spindle by a positioning motor.
An example of the carriage is disclosed in U.S. Pat. No. 4,167,765. The carriage of this disclosure includes carriage arms, a head suspension attached to a front end of each carriage arm, a head attached to the head suspension, and a slider attached to the head. When the disks are rotated at high speed, the sliders slightly float from the disks, and air bearings are formed between the disks and the sliders.
The head suspension includes a load beam made of a precision thin plate spring, a flexure made of a very thin plate spring fixed to a front part of the load beam by, for example, laser welding, and a plate fixed to a base of the load beam by, for example, laser welding. The plate is fixed to a head suspension fitting face of the carriage arm.
FIG. 21 shows a structure to fix a head suspension to a carriage arm according to a related art disclosed in Japanese Patent Laid Open Publication No. 2001-176224. A boss 101 is formed separately from a plate 103. The boss 101 may have a flange and a protrusion. The plate 103 is a base to be attached to the carriage arm 111.
In FIG. 21, the boss 101 has a base 105 and a protrusion 107. The base 105 is arranged in a through hole 109 formed in the plate 103. The base 105 has a support periphery 115. The support periphery 115 has a support face 117 that fits in the through hole 109 of the plate 103. The boss 101 is fixed to the plate 103 by, for example, laser welding. An end face 124 of the boss 101 is substantially flush with a second face 121 of the plate 103. The protrusion 107 is fitted into a hole 113 of the carriage arm 111. The protrusion 107 has a fitting periphery 119. On the second face 121 of the plate 103, a base of a resilient material 123 is fixed by, for example, laser welding.
To attach the plate 103 to the carriage arm 111, a first face 125 of the plate 103 is adjusted to a surface 127 of the carriage arm 111, and the protrusion 107 of the boss 101 is fitted into the hole 113 of the carriage arm 111.
A jig 129 is set on the base 105 of the boss 101, to hold the boss 101 against the carriage arm 111. From the direction of an arrow mark, a steel ball is passed through a hole 131 of the boss 101, to expand the hole 131 and plastically deform the protrusion 107. As a result, the fitting periphery 119 of the boss 101 is pressed to the hole 113 of the carriage arm 111, and the plate 103 is fixed to the carriage arm 111 through the boss 101.
The boss 101 must have a proper softness for the above-mentioned plastic deformation. The plate 103 must have proper flatness and high hardness so that it may precisely and strongly be fixed to the carriage arm 111.
To reduce weight, the thinner the plate 103, the better. For example, the plate 103 is thinned to 150 ì m from a conventional thickness of 300 ì m. If the boss 101 and plate 103 must be in one body, they will be formed by pressing a plate material into respective thicknesses. Forming the plate 103 by pressing, however, deteriorates the flatness thereof. Employing a thin plate material to form the plate 103 having a thickness of, for example, 150 ì m makes the thickness of the boss 101 insufficient.
To cope with this problem, the boss 101 and plate 103 of FIG. 21 are formed separately from each other. The boss 101 is made of metal softer than metal for the plate 103, so that the boss 101 may easily be deformed and fixed to the carriage arm 111. The plate 103 formed independently of the boss 101 needs no pressing to adjust the thickness thereof, thereby securing flatness. The plate 103 may be made of hard metal, to improve the attaching accuracy and strength of the plate 103 to the carriage arm 111. The boss 101 may have an optional shape without regard to the thickness of the plate 103. The plate 103 may be made thinner to further reduce the total weight of the head suspension.
The structure mentioned above, however, has some problems. The end face 124 of the boss 101 is flush with the second face 121 of the plate 103, and therefore, reaction force from the jig 129 is also applied to the plate 103, to make the support of the boss 101 by the jig 129 insufficient. When a steel ball is passed through the hole 131 to deform the protrusion 107, the boss 101 may incline relative to the carriage arm 111.
If the fitting periphery 119 of the boss 101 is pressed to the hole 113 of the carriage arm 111 with the boss 101 inclining relative to the carriage arm 111, the plate 103 fixed to the carriage arm 111 will be oblique relative to the carriage arm 111. This results in deteriorating the attaching accuracy of the plate 103 to the carriage arm 111, the positioning accuracy of a slider on a disk, and the vibration characteristics of the head suspension.
The inaccurate connection of the boss 101 to the hole 113 of the carriage arm 111 also decreases the attaching strength of the boss 101 to the carriage arm 111.